1. Field of the Invention
The present invention relates to a constant-voltage circuit which generates a stable voltage.
2. Description of the Related Art
A reference voltage generation circuit using a bipolar transistor or a reference voltage generation circuit using a field effect transistor has hitherto been known (for example, see Japanese Unexamined Patent Application Publication Nos. 2010-49422 and 2010-108419). In general, a reference voltage generation circuit using a bipolar transistor has a feature of stable activation with a constant voltage and little influence of a process variation. A reference voltage generation circuit using a field effect transistor has a feature of low power consumption.
From the features of the reference voltage generation circuits, in a digital circuit which needs to rapidly generate a constant voltage, a constant-voltage circuit which includes a reference voltage generation circuit using a bipolar transistor is frequently used. However, since the reference voltage generation circuit includes the bipolar transistor which is driven by a base current, there is a problem in that power consumption of the constant-voltage circuit increases. In order to suppress power consumption, if a reference voltage generation circuit using a field effect transistor is used, it is difficult to activate the reference voltage generation circuit with a stable voltage. As described above, in the constant-voltage circuit of the related art, it is difficult to achieve both activation with a stable voltage and low power consumption.